15,567 research outputs found

    Leptonic Decays of BB- and DD-Mesons

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    The present status of lattice calculations of fDf_D, fBf_B and some mass splittings are discussed. When one includes the uncertainties due to discretization errors, the results do not yet have a sufficient precision to be relevant to phenomenological applications. There are, however, good prospects of cutting down the uncertainties by a factor of 2 or more soon.Comment: 8 pages, postscript included all figures, uuencode

    Non-perturbative renormalization of the axial current with improved Wilson quarks

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    We present a new normalization condition for the axial current, which is derived from the PCAC relation with non-vanishing mass. Using this condition reduces the O(r_0 m) corrections to the axial current normalization constant Z_A for an easier chiral extrapolation in the cases, where simulations at zero quark-mass are not possible. The method described here also serves as a preparation for a determination of Z_A in the full two-flavor theory.Comment: 3 pages, 3 figures, Lattice2003(improve

    A dynamical and kinematical model of the Galactic stellar halo and possible implications for galaxy formation scenarios

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    We re-analyse the kinematics of the system of blue horizontal branch field (BHBF) stars in the Galactic halo (in particular the outer halo), fitting the kinematics with the model of radial and tangential velocity dispersions in the halo as a function of galactocentric distance r proposed by Sommer-Larsen, Flynn & Christensen (1994), using a much larger sample (almost 700) of BHBF stars. The basic result is that the character of the stellar halo velocity ellipsoid changes markedly from radial anisotropy at the sun to tangential anisotropy in the outer parts of the Galactic halo (r greater than approx 20 kpc). Specifically, the radial component of the stellar halo's velocity ellipsoid decreases fairly rapidly beyond the solar circle, from approx 140 +/- 10 km/s at the sun, to an asymptotic value of 89 +/- 19 km/s at large r. The rapid decrease in the radial velocity dispersion is matched by an increase in the tangential velocity dispersion, with increasing r. Our results may indicate that the Galaxy formed hierarchically (partly or fully) through merging of smaller subsystems - the 'bottom-up' galaxy formation scenario, which for quite a while has been favoured by most theorists and recently also has been given some observational credibility by HST observations of a potential group of small galaxies, at high redshift, possibly in the process of merging to a larger galaxy (Pascarelle et al 1996).Comment: Latex, 16 pages. 2 postscript figures. Submitted to the Astrophysical Journal. also available at http://astro.utu.fi/~cflynn/outerhalo.htm

    Evaluation of a contact-analog display in landing approaches with a helicopter

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    Evaluation of contact analog display in landing approaches with helicopter

    CDM, Feedback and the Hubble Sequence

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    We have performed TreeSPH simulations of galaxy formation in a standard LCDM cosmology, including effects of star formation, energetic stellar feedback processes and a meta-galactic UV field, and obtain a mix of disk, lenticular and elliptical galaxies. The disk galaxies are deficient in angular momentum by only about a factor of two compared to observed disk galaxies. The stellar disks have approximately exponential surface density profiles, and those of the bulges range from exponential to r^{1/4}, as observed. The bulge-to-disk ratios of the disk galaxies are consistent with observations and likewise are their integrated B-V colours, which have been calculated using stellar population synthesis techniques. Furthermore, we can match the observed I-band Tully-Fisher (TF) relation, provided that the mass-to-light ratio of disk galaxies, (M/L_I), is about 0.8. The ellipticals and lenticulars have approximately r^{1/4} stellar surface density profiles, are dominated by non-disklike kinematics and flattened due to non-isotropic stellar velocity distributions, again consistent with observations.Comment: 6 pages, incl. 4 figs. To appear in the proceedings of the EuroConference "The Evolution of Galaxies: II - Basic Building Blocks", Ile de La Reunion (France), 16-21 October 2001 (Slightly updated version). A much more comprehensive paper about this work with links to pictures of some of the galaxies can be found at http://babbage.sissa.it/abs/astro-ph/020436

    How to Accurately Extract the Running Coupling of QCD from Lattice Potential Data

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    By (a) using an expression for the LATTICE potential of QCD in terms of a CONTINUUM running coupling and (b) globally parameterizing this coupling to interpolate between 2- (or higher-) loop QCD in the UV and the flux tube prediction in the IR, we can perfectly fit lattice data for the potential down to ONE lattice spacing and at the same time extract the running coupling to high precision. This allows us to quantitatively check the accuracy of 2-loop evolution, compare with the Lepage-Mackenzie estimate of the coupling extracted from the plaquette, and determine the scale r0r_0 ten times more accurately than previously possible. For pure SU(3) we find that the coupling scales on the percent level for ÎČ≄6\beta \geq 6.Comment: 3 pages Latex incl. 2 figures, uses espcrc2.sty, contribution to LATTICE '9

    Evaluation of a closed-circuit television display in landing operations with a helicopter

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    Evaluating closed circuit television display in helicopter landing operation

    Breast cancer: Monitoring response to neoadjuvant chemotherapy using Tc-99m sestamibi scintimammography

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    Background: Aim of the study was to assess the value of scintimammography using Tc-99m sestamibi in the evaluation of tumor response to neoadjuvant chemotherapy. Material and Methods: Results were calculated for 9 patients undergoing neoadjuvant chemotherapy. Scintimammography using 740 MBq Tc-99m sestamibi was performed before, during and after chemotherapy, and sestamibi uptake was scored visually and semiquantitatively to evaluate tumor response. Results: In the case of complete response (n = 3) sestamibi uptake decreased 8 days after beginning neoadjuvant chemotherapy and normalized in the following course. Focal uptake decreased more slowly in patients with partial response (n = 3), who showed clear, persisting tracer accumulation after therapy. The patients without response (n = 3) showed a persisting high tumor activity even after chemotherapy was completed. Conclusions: The preliminary data suggest that in contrast to other imaging modalities scintimammography appears to yield early information regarding tumor response to neoadjuvant chemotherapy
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